Explosives used in military combat may be initiated by detonation devices. Due to the destructive nature of explosives, these detonation devices may incorporate various safety features to avoid premature detonation. Explosive materials may be ignited in several different ways. Typically, explosive materials have been ignited by flame ignition (e.g., fuzes or ignition of a priming explosive), impact (which often ignites a priming explosive), chemical interaction (e.g., contact with a reactive or activating fluid), or electrical ignition. Electrical ignition may occur in two distinct ways, as by ignition of a priming material (e.g., electrically ignited blasting cap or priming material) or by direct energizing of an explosive mass by electrical power.
Remote activation systems for detonating explosives have been used widely in the field of military and industrial demolition applications. In the past, initiation devices have been used to generate an electrical impulse for initiating detonation. For example, a blasting cap used in conjunction with an explosive charge (e.g., pentaerythritol tetranitrate (PETN), C4, etc.) can be electrically connected to output terminals of the initiation device using electrical conductors. In many instances, the conductors can be several hundred meters long to separate the initiation device and the explosive. In such an arrangement, the explosive assembly is sensitive to electrical conditions, such as electromagnetic interference (EMI) and electrostatic discharge (ESD). As a result of this sensitivity, premature detonation of the explosive charge has been known to occur with unacceptable frequency. The results of premature detonation can include unintended damage and/or unintended personal injury or death.
Attempts have been made to avoid using electrical conductors to deliver explosion initiating energy from the initiation device to the explosive change. In one attempt a mechanical arm driven by a solenoid was used to initiate a device that propagates a chemical reaction from initiator to explosive. Such an attempt is described in U.S. Pat. No. 6,546,873 which discloses a transmitter that transmits a detonation signal to a receiver. The receiver can be configured to deliver an electrical output in response to a received detonation signal. Such electrical output can be used to electrically excite a blasting cap via conductors. But, as indicated above, if the conductors have any appreciable length (e.g., 50 meters or more), ambient electrical conditions (e.g., an atmospheric electrical storm) can cause premature detonation of the explosive.
Another attempt is described in U.S. Pat. No. 7,451,700 which discloses a detonation initiator including a linear actuator assembly having a core with a permanent magnet. The linear actuator assembly propels the core along the longitudinal axis of the linear actuator assembly when the charge on the capacitor reaches a charge threshold. The core includes a firing pin that mechanically strikes a primer connected to an open end of a shock tube. Striking the primer in results in chemical activation of the primer and, in turn, begins ignition of combustible material in the shock tube. However, such a configuration requires that an open end of the shock tube be inserted into the detonation initiator in order to be initiated. The end of the shock tube must be cut or otherwise opened and inserted into the device adjacent to the primer. Exposing the end of a shock tube may be undesirable as the shock tube may become contaminated or exposed to other undesirable environmental condition. Further, if the partially exposed shock tube is not detonated, all or part of the unused shock tube (including any detonation devices connected to the shock tube) may not be reused and will be wasted. As also illustrated in U.S. Pat. No. 7,451,700, the connection between the shock tube and primer and position of the shock tube within the initiator may be critical in assuring proper ignition of the shock tube. As such, the detonation initiator disclosed therein requires proper placement of the shock tube within the initiator and may not be applicable for use with shock tubes of varying sizes.